Advances in molecular genetics have made it possible to consider treating certain genetic diseases by somatic cell gene therapy, i.e. by transferring copies of a normal gene into the somatic cells of a patient in order to restore the function of the gene that is involved. The field of gene therapy is in its infancy, therefore, it is advantageous to investigate the efficacy of gene therapy in animal models of human genetic disease. A group of animal models that can be used for this purpose are cats and dogs with mucopolysaccharidoses (MPS diseases), which are deficiencies in the activities of lysosomal enzymes. The proposed experiments will focus on the cat model of MPS VI, Maroteaux-Lamy Syndrome, which is a deficiency in arylsulfatase-B (ASB) activity. Two of the prerequisites for efficatious gene therapy are that the gene must be efficiently transferred to a sufficient number of target cells in the patient and that the transferred gene must be efficiently expressed in the target cells in vivo. In the proposed experiments, the ASB gene will be inserted into retroviral vectors (e.g. N2) which are very efficient in transferring genes into target cells. Several vectors, containing various transcriptional promotors, will be constructed in order to evaluate their relative efficiency of expression and virus production. The ASB gene will be transferred to MPS VI cells in vitro by infection with the recombinant viruses and the target cells will be assayed for enzyme activity and RNA expression from the transferred gene. The proposed experiments are necessary before expression of the gene in vivo can be evaluated through actual attempts at gene therapy in the MPS VI cats. Additionally, constructing retroviral vectors that contain the ASB gene will make it possible to directly investigate the molecular mechanisms of pathogenesis within MPS VI cells by introducing a functional gene into a diseased cell. Furthermore, the proposed experiments will enable the investigators to transfer the recombinant DNA technology to studies on gene therapy and molecular mechanisms of pathogenesis in several other animal models of genetic diseases.